At least 178 teachers and principals at nearly four dozen schools in Atlanta have been implicated in what is likely the largest cheating scandal in U.S. history to date.

The report found that teachers, principals and administrators were both helping students on the state’s standardized test, the Criterion-Reference Competency Test, and correcting incorrect answers after students had turned the tests in. Eighty-two educators confessed to the allegations detailed in the report from the Georgia Bureau of Investigations.

Calling it a “dark day” for Atlanta Public Schools, Mayor Kasim Reed said the yearlong investigation “confirms our worst fears … There is no doubt that systemic cheating occurred on a widespread basis in the school system. Further, there is no question that a complete failure of leadership in the Atlanta Public School system hurt thousands of children who were promoted to the next grade without meeting basic academic standards.”

The investigation tarnishes the record of Superintendent Beverly Hall, who was named national Superintendent of the Year in 2009, due in large part to reported gains in the district. The 800-page report shows some educators reported cheating in their schools, but Hall and other school officials ignored the claims, and in some cases, punished those who came forward. Hall stepped down at the end of her contract on June 30.

Though shocking, the Atlanta cheating scandal is just the latest (and largest) among at least a dozen other cheating controversies that have been unearthed across the country. One especially noteworthy case was that of D.C. Public Schools, which at the time was led by Chancellor Michelle Rhee. Earlier this year, a USA Today article detailed an unusual level of “erasures,” which is the term for wrong answers that have been erased and changed to right.

Increasing incidents of teachers cheating has led some to question whether the pressure to score well on the standardized tests required under No Child Left Behind are tempting teachers to cheat as, under the federal law, teachers can face cuts to their salary or even potentially lose their jobs if test scores do not meet certain standards.